The present invention relates to an automatic workpiece engaging apparatus for use in a grinding machine, and more particularly to an automatic workpiece engaging apparatus capable of automatically taking a workpiece or gear accurately into mesh with a grinding wheel having helical teeth, of preventing different types of workpieces from being ground, of detecting improper workpieces, and of automatically smoothly correcting any deviation from the workpiece of the grinding wheel when the latter is shifted to displace an effective area of a grinding edge thereof.
There has been employed in the art an apparatus for grinding a number of teeth of a workpiece such as a gear while in mesh with a grinding wheel having helical teeth on an outer peripheral surface thereof. No desired finished gear can be achieved unless the grinding wheel and the gear are rotated in synchronism since the gear teeth would not be ground uniformly by the grinding wheel in the absence of synchronous rotation of the grinding wheel and the gear. To rotate the grinding wheel and the gear in synchronism, the following relation has to be met: EQU The number of r.p.m. of the grinding wheel.times.the number of teeth of the grinding wheel=the number of r.p.m. of the gear.times.the number of teeth of the gear.
For grinding a gear with a grinding wheel while meeting the above requirement, it has heretofore been necessary to manually bring the gear and the grinding wheel into initial mesh with each other at the time the gear and the grinding wheel are at rest. When it is desired to grind a number of gears of the same dimensions, the grinding wheel is required to be stopped each time a new gear has to be ground. The time required to stop the grinding wheel is lengthy and wasteful especially where the grinding wheel rotates at a high speed and has a large inertia. The prior procedure is also disadvantageous in that it does not lend itself to automatic continuous grinding operation.
When grinding a number of gears in succession, there is sometimes a tendency for different types of gears to be included in a batch of gears readied for grinding operation, such different gears having the same module but a different number of gear teeth, for example. If such different kinds of gears that cannot be discriminated at a glance are included and ground, they will not be properly ground and the overall grinding process will greatly be disrupted.
In conventional gear grinding machines of the screw roll type, it is customary to shift a grinding wheel in the direction of its own axis periodically for uniform utilization of all helical teeth on the grinding wheel. By shifting the grinding wheel, the position where it meshes with the gear is displaced so that the helical teeth on the grinding wheel will be prevented from localized damage. One problem with the prior grinding wheel shifting procedure is however that when the grinding wheel is shifted, there is developed a deviation between the grinding wheel and the gear, and they are not in proper mesh with each other.